Can covers are produced in the form of disks of sheet metal annually in hundreds of millions of pieces and must be handled upon manufacture for incorporation into can-closing equipment and the like in stacks.
Although can covers represent a mass-produced article, it has been necessary heretofore to provide a large number of systems for the manufacture, handling, transportation and intervening storage of the stacks of covers.
Indeed, between the fabrication of the sheet metal disk and its application to the can, there are many steps in the process which involve handling of the can cover and for the various purposes the covers have been provided, the handling, guidance and manipulation techniques have varied.
As noted, the disks are generally handled in the form of stacks, this term being utilized to refer to a multiplicity of the disks in adjacent relationship, whether the column of disks is upright, horizontal or in some other orientation, the stack being provided at the disk-fabrication site, at the container-closing site and hence in the packaging machine, and at the various treatment and storage sites therebetween.
Consequently, it is necessary to transport stacks of the sheet metal disks between these locations and, in practice, the transport paths between the various locations can exceed 100 meters in length. Because the transport path must be capable of delivering the stacks to or receiving the stacks from a variety of locations, this path is frequently curved, i.e. can have a variety of directional changes in it.
It is known, for the transport of stacks of sheet metal disk-shaped elements to provide a channel which is enclosed in an inversely-shaped shell-like cage and to hold sections of the channel together with arc-shaped transverse bars which can be individually connected to the longitudinal channel-forming bars.
This system has been found to be disadvantageous because it requires time-consuming attachment and mounting steps. It is also relatively expensive, difficult to maintain because of the time-consuming mounting and dismounting operations which are necessary, and prone to malfunction since it must be adjusted with precision.
Indeed, if precise attachment of the channel-forming member and its mounting members is not ensured, a reliable guidance of the stack through the channel cannot be guaranteed and the transport process will be fraught with jamming and interruption.
Furthermore, the disk-shaped metal elements, which are usually composed of aluminum, tend to frictionally interact with the channel walls which may be composed of the same or other materials, causing rapid wear and deterioration thereof and increasing the need for maintenance with the drawbacks enumerated above.